This invention relates to novel forms of 1,3-dibromo-5,5-dimethylhydantoin which, by virtue of their characteristics and physical properties, are superlative biocidal water-treating agents and brominating agents.
As used herein the terms xe2x80x9chalogenxe2x80x9d, xe2x80x9chalogenatedxe2x80x9d, and xe2x80x9chaloxe2x80x9d are with reference to bromine or chlorine, or both.
1,3-Dihalo-5,5-dialkylhydantoins, especially 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, 1-bromo-3-chloro-5,5-dimethylhydantoin, and 1-chloro-3-bromo-5,5-dimethylhydantoin, or mixtures of two or more of them, are biocidal agents for use in water treatment. These compounds are, in general, sparingly soluble in water. Each of these compounds except 1,3-dibromo-5,5-dimethylhydantoin, has been supplied in compacted solid forms such as granules, tablets, or briquettes, and delivered into the water being treated by means of water flow through an erosion feeder. The compacted forms of the 1,3-dichloro-5,5-dimethylhydantoin have been produced using a binder. Of the three manufacturers of compacted forms of N,Nxe2x80x2-bromochloro-5,5-dimethylhydantoin, two such manufacturers are known to utilize a binder in producing the compacted forms. The technology used by the other manufacturer to produce such compacted forms has not been disclosed. So far as is known, never before has 1,3-dibromo-5,5-dimethylhydantoin powder been converted into a compacted form by any method.
Over the years considerable effort has been devoted to the search for improved methods for producing such compounds. In U.S. Pat. No. 2,971,960 N-brominated compounds such as N-brominated 5,5-di-lower-alkyl hydantoins are formed by treating the alkylhydantoin with bromine in an acidic aqueous solution containing hypochlorite, preferably at a pH between 1 and 4. However, the method of choice has been halogenation of the alkylhydantoin in a basic aqueous medium. Almost invariably the halogen has been introduced into, or formed in situ in, the aqueous medium containing the alkylhydantoin. See in this connection U.S. Pat. Nos. 2,398,598; 2,779,764; 2,868,787; 2,920,997; 2,971,959; 3,121,715; 3,147,259; 4,532,330; 4,560,766; 4,654,424; 4,677,130; 4,745,189; PCT
Publication No. WO 97/43264, published Nov. 20, 1997; Orazi and Meseri, Anales Assoc. Quim. Argentina, 1949, 37, 192-196; Orazi and Meseri, Anales Assoc. Quim. Argentina, 1950, 38, 5-11; Corral and Orazi, J. Org. Chem., 1963, 23, 1100-1104; Jolles, Bromine and its Compounds, Ernest Benn, London, 1966, p. 365; and Markish and Arrad, Ind. Eng. Chem. Res., 1995, 34, 2125-2127.
The N,Nxe2x80x2-dihalogenated dialkylhydantoin products formed by such processes are formed as powdery solids. For use in many applications the dry powders need to be converted into larger forms such as granules, tablets, or briquettes. This in turn has presented problems associated with providing densified or compacted products with sufficient strength to withstand the physical stresses encountered in packaging, conveying, handling, shipping, storage, and use. The nature of these problems have been described, for example, in U.S. Pat Nos. 4,532,330; 4,560,766; 4,654,424; 4,677,130; 4,745, 189; and 5,565,576. The approaches described in these patents for alleviating one or more such problems involve use of additional or other materials. Thus in U.S. Pat. Nos. 4,532,330 and 4,621,096, halogenated dimethylhydantoins are mixed with calcium chloride and water, and the mixture is compacted by compression into the desired shape. In U.S. Pat. Nos. 4,560,766 and 4,654,424, halogenated ethylhydantoins are used instead of halogenated dimethylhydantoins and are compacted as such, or are melt blended with halogenated dimethylhydantoins. U.S. Pat. No. 4,677,130 describes forming dry blends of the halogenated dimethylhydantoin with particulate alkali metal or alkaline earth metal salt followed by compression to form a compacted product such as a tablet. PCT Publication No. WO 97/43264 describes the use of 1,3-bromochloro-5-methyl-5-propylhydantoin as a binder in making compacted forms of halogenated hydantoins.
U.S. Pat. No. 4,745,189 describes formation of halogenated dimethylhydantoin by halogenating the hydantoin in an aqueous mixture under alkaline conditions in the presence of a halogenated alicyclic organic compound such as dichloromethane. The Examples of the patent describe the formation of N,Nxe2x80x2-bromochloro-5,5-dimethylhydantoin products comprised of large particles. However, so far as is known, no 1,3-dibromo-5,5-dimethyl-hydantoin having an average particle size of at least 175 microns has been described anywhere in the prior art.
U.S. Pat. No. 4,560,766 teaches that halogenated dimethylhydantoin per se cannot be used for making low-dust powders, granules, tablets, flakes, compacted forms, cast forms, and carrier-coated products without the aid of a binder.
Despite extensive research efforts in the field, a number of additional serious problems remain unsolved. For one thing, processes utilized in the production of 1,3-dihalo-5,5-dimethylhydantoins form powders which have the undesirable characteristic of producing large quantities of irritating, corrosive dusts when handled and used. Further, products formed from bromine-containing 1,3-dihalo-5,5-dimethylhydantoin, which are widely distributed as consumer products, have aesthetic properties that are less than desirable. Typically, products produced from such bromine-containing 1,3-dihalo-5,5-dimethylhydantoins have a distinct yellow coloration.
Other remaining unsolved problems relating to previously known 1,3-dihalo-5,5-dimethylhydantoins involve their lack of acceptable flowability characteristics. In particular, 1,3-dihalo-5,5-dimethylhydantoin powders exhibit high interparticulate friction and thus cannot be readily discharged from feed hoppers or be transferred without xe2x80x9cbridgingxe2x80x9d or xe2x80x9carchingxe2x80x9d when passing through conduits or screw conveyors. In such operations, xe2x80x9cbridgingxe2x80x9d or xe2x80x9carchingxe2x80x9d (which are synonymous terms) is a condition in which the particles stick together without fusing to form lumps or clumps or balls of particulate material, which in turn seriously interfere with or impede further flow of the material. Another problem associated with 1,3-dihalo-5,5-dimethylhydantoin powders is their strong tendency to undergo xe2x80x9cratholingxe2x80x9d when being discharged from a conical hopper or feeder. This means that, rather than discharging evenly from the device, the powder discharges from the center only, leaving an annular mass of the powder suspended against the interior sloping conical sides of the device. In severe cases, it becomes necessary to release such suspended powder by striking the exterior of the device with a hammer or baseball bat.
It would be of considerable advantage if 1,3-dibromo-5,5-dimethylhydantoins could be provided as powders having little or no dusting characteristics. It would also be of great advantage to provide particulate 1,3-dibromo-5,5-dimethylhydantoins useful for making granules, caplets, tablets, flakes, compacted forms, cast forms, and carrier-coated products without the aid of a binder, and without use in the production process of any organic halogen compound such as dichloromethane. Moreover, the provision of 1,3-dibromo-5,5-dimethylhydantoins having an average particle size larger than available heretofore would be a most welcome contribution to the art. Still other features of considerable advantage in the art would be the provision of 1,3-dibromo-5,5-dimethylhydantoins having superior flowability characteristics and more appealing aesthetic properties.
This invention involves the discovery, inter alia, of 1,3-dibromo-5,5-dimethylhydantoin particulate solids having unique physical properties. Such 1,3-dibromo-5,5-dimethylhydantoin particulate solids can be produced by the process described in commonly-owned U.S. application Ser. No. 09/484,844, filed Jan. 18, 2000.
More particularly, this invention provides 1,3-dibromo-5,5-dimethylhydantoin particulate solids having larger average particle sizes than have been available heretofore in the marketplace. It has been discovered that the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention are ideally suited for compaction and tableting in as much as these operations can be conducted without need of a binder of any kind. Moreover, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention have little or no dusting characteristics, have superior flowability properties, and possess more appealing aesthetic qualities than commercially-available products of this type.
Accordingly, this invention provides, inter alia, novel 1,3-dibromo-5,5-dimethylhydantoin particulate solids having large average particle sizes, shape-retentive pressure compacted articles produced from binder-free 1,3-dibromo-5,5-dimethylhydantoin particulate solids, and methods of producing such shape-retentive compacted articles from such binder-free 1,3-dibromo-5,5-dimethylhydantoin particulate solids.
One of the unprecedented properties of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their large average particle size. Unlike prior forms of 1,3-dibromo-5,5-dimethylhydantoin which, when obtained from a supplier of laboratory-sized quantities of chemicals for laboratory usage had an average particle size of about 162 microns, and from two large scale producers, had respective average particle sizes of about 45 and about 65 microns, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention have average particle sizes of at least about 175 microns, and preferably at least about 200 microns. In fact, 1,3-dibromo-5,5-dimethylhydantoin can now be provided having an average particle size of over 500 microns. A highly desirable manifestation of the large average particle sizes of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their freedom from the undesirable characteristic of producing large quantities of irritating, corrosive dusts when handled and used. In operations performed to date, the quantities of dust produced during processing have been remarkably low.
Another of the unprecedented properties of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their compactibility. Not only can they be compacted without use of a binder, but in addition, the compacted forms, even though devoid of a binder, are shape retentive, and in addition have remarkable crush strength. In fact, this invention involves the further discovery that prior 1,3-dibromo-5,5-dimethylhydantoin powders cannot be removed from a tableting die without breakage. In sharp contrast, the pressure compacted larger average particle size 1,3-dibromo-5,5-dimethylhydantoin of this invention can be removed from the die without any breakage occurring. In particular, prior smaller average particle size 1,3-dibromo-5,5-dimethylhydantoin, when released or extracted from a tableting die, xe2x80x9cdelaminatexe2x80x9d, meaning that the compacted agglomerate breaks apart into smaller pieces, whereas the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can be directly converted into shape-retentive tablets of acceptably high physical integrity, without any prior treatment to impart compactibility to the solids.
Moreover, when pressure compacted into granules, tablets, briquettes, or other relatively small shapes, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention have excellent physical properties for use in water-treatment systems. The shapes erode at slow, but essentially constant, rates when maintained in a constant flow of water. They withstand the customary physical stresses encountered- in packaging, conveying, handling, shipping, storage, and use. The compacted solid forms of this invention produced directly from the larger particle sized 1,3-dibromo-5,5-dimethylhydantoin particulate solids have excellent crush strength even when formed without a binder. In fact, such solid forms when produced with suitable binders have even greater crush strength, and can be converted into even larger non-friable shaped articles such as toilet bowl and swimming pool pucks.
Still another unprecedented property of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their excellent flowability characteristics. In particular, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention exhibit low interparticulate friction and thus can be readily discharged from feed hoppers, and in addition such particulate solids can be transferred without xe2x80x9cbridgingxe2x80x9d or xe2x80x9carchingxe2x80x9d when passing through conduits or screw conveyors. In such operations, few, if any, lumps or clumps or balls of particulate material are formed, and thus, little or no interruption of product flow is experienced. Further, in hopper discharging operations, little or no xe2x80x9cratholingxe2x80x9d occurs.
Yet another exceedingly desirable property of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their unprecedented creamy white almost white appearance. For example, this invention makes possible the provision of 1,3-dibromo-5,5-dimethylhydantoin particulate solids having a Yellowness Index of about 15 or less. This compound previously available in the marketplace has a distinct yellow coloration which is aesthetically less desirable.
At present the only known way of preparing the novel and eminently useful 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention involves use of the process technology described in commonly-owned co-pending application No. 09/484,844, filed Jan. 18, 2000. If in the future other methods can be discovered that produce 1,3-dibromo-5,5-dimethylhydantoin particulate solids having one or more of the unique characteristics of the present invention, such 1,3-dibromo-5,5-dimethylhydantoin particulate solids will of course fall within the scope of the present invention as set forth in the appended claims.
In converting the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention into granules, conventional processing equipment can be used under the usual operating conditions. Typically, 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention, with or without a binder, are compressed into sheet form by means of a roll compactor. This sheet in turn is broken up into small granules by a mechanical device, such as a Chilsonator(copyright) breaker (The Fitzpatrick Company, Elmhurst, Ill.). The granules are then classified by screening into the desired size range. Undersized granules are typically recycled to the roll compactor, whereas oversized granules are recycled to the breaker device.
Highly suitable apparatus for producing granulated 1,3-dibromo-5,5-dimethylhydantoin is the proprietary MS-75 compactor system (Hosokawa Bepex, Minneapolis, Minn.).
The formation of tablets and other compressed shapes such as briquettes from the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can utilize known processing equipment and, for the most part, known procedures. However, in conducting compaction of the 1,3-dibromohydantoin particulate solids of this invention in the absence of a binder, it is important that the compaction pressure be sufficient to induce plastic deformation and interparticulate binding of the particles. At the same time, the compaction pressure should not be so great as to produce a compacted product which delaminates on expulsion from the die. Typically, suitable compaction pressures in the practice of this invention will fall within the range of about 1000 to about 30,000 psi, and preferably in the range of about 5000 to about 25,000 psi. Such compaction can be conducted using, for example, a rotary tableting press operated at conventional rotational speeds, e.g., about 20 rpm. Another method for accomplishing the compaction is by means of pressure extrusion through a die orifice, while concurrently shearing the extrudate to produce compacted shapes of the desired size. In such operations, the compaction pressures within the die should be sufficient to induce plastic deformation and interparticulate binding of the particles, but insufficient to produce a compacted product which, when extruded, undergoes an elastic recovery of a magnitude that causes delamination of the compacted extrudate.
In operations conducted on a small scale using manually filled dies, 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention having an average particle size of greater than about 175 microns have been successfully compacted into tablets without employment of any binder. The tablets when released from the dies were intact and exhibited no visual surface imperfections.
The 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can also be directly converted without use of a binder into whole briquettes utilizing conventional briquetting rolls operated under conventional conditions. In such operations, pressures in the range of about 1000 to about 30,000 psi are typical; more preferably, the pressures are in the range of from about 5000 to about 25,000 psi. As in the case of pressure compaction of tablets, the compaction pressure should be sufficient to induce plastic deformation and interparticulate binding of the particles, but insufficient to produce a compacted product which undergoes an elastic recovery of a magnitude causing delamination of the compacted article on exiting the rolls.
The compaction operations, whether performed in a die, by extrusion through an orifice of a die, or by roll compaction is typically conducted at ambient room temperatures. However, it is possible to either cool or warm the material being subjected to compaction. This can be accomplished either by refrigerating or directly heating the product before introducing it into the compaction apparatus, or by chilling or heating the apparatus itself such as, for example, by using rolls equipped with heating or cooling coils or other means for effecting temperature regulation. The compaction operation itself can, and in many cases does, result in generation of heat within the compacted shape. Generally speaking, the compaction operations pursuant to this invention can be performed at temperatures in the range of about 5 to about 80xc2x0 C.
It will be understood and appreciated that departures from the numerical ranges given herein for pressures and temperatures are permissible in the practice of this invention, whenever such departures are deemed necessary or desirable, provided only that such departures do not materially affect in an adverse manner the processing or the properties of the product being produced.
Typically, compacted products of this invention other than granules, e.g., tablets, briquettes, and pucks, formed without use of a binder, will have a crush strength in the range of from about 25 to about 75 pounds per inch of thickness when measured as described hereinafter. Thus, this invention provides tablets which have crush strengths, when measured in the diametral direction (i.e., when a disc-shaped tablet stands on its edge), of from about 25 to about 75 pounds per inch of thickness. In the case of briquettes or other non-disc-shaped articles including granules, the crush strength should be measured in the longitudinal direction, (i.e., with the article standing such that its longest dimension is in the vertical position). Thus, for example, briquettes of this invention have a crush strength of from about 25 to about 75 pounds per inch of thickness when measured in this manner. Granules of this invention will typically have somewhat lower crush strength which, nevertheless, is sufficient for most applications in which granules are to be used. Thus, it is now possible to provide, for the first time, binder-free compacted products having the strength needed to withstand the physical stresses encountered in packaging, conveying, handling, shipping, storage, and use.
When converted into tablets, briquettes, pucks, and other compacted shapes with use of a suitable binder, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention result in compacted forms of even greater crush strength. Binders suitable for such use include the normally solid, fatty amides such as N,Nxe2x80x2-ethylenebisstearamide and related compounds described in U.S. Pat. No. 5,565,576. Markedly superior binding agents for use with the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention are the micronized polyolefin waxes and the micronized polyfluorocarbon waxes described in commonly-owned co-pending application Ser. No. 09/487,816, filed Jan. 18, 2000.
By use of suitable binders, compacted products with crush strengths in the range of from about 60 to about 200 pounds per inch of thickness can be formed. Thus, these compacted products are capable of withstanding, to a greater extent, the physical stresses encountered in packaging, conveying, handling, shipping, storage, and use.
Granules, tablets, and briquettes produced from 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention are of particular utility as biocidal agents for use in swimming pools spas, toilet bowl cleaners, cooling towers, air washer systems, wastewater, pulp and paper processing operations, oil field applications, and decorative fountains. Procedures utilizing 1,3-dibromo-5,5-dimethylhydantoin as a biocide and sanitizer in the treatment of aqueous systems or water and its use as an agent to eradicate or reduce biofilm on surfaces contacted with aqueous media are more fully described in commonly-owned copending application Ser. No. 09/484,938, filed Jan. 18, 2000.
As indicated above, one of the unique characteristics of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention is their unprecedented larger average particle size. So far as is known, 1,3-dibromo-5,5-dimethylhydantoin particulate solids with an average particle size of at least about 175 microns has never before been available, and such particulate solids having at least such average particle size constitute embodiments of this invention. Preferred 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention have an average particle size of at least about 200 microns, more preferably at least about 300 microns, still more preferably at least about 400 microns, with 1,3-dibromo-5,5-dimethylhydantoin particulate solids having an average particle size of at least about 500 microns being particularly preferred. Even more preferred are the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention having an average particle size of about 600 microns or more. In each case, the foregoing particle sizes are expressed in terms of 1,3-dibromo-5,5-dimethylhydantoin particulate solids which have not been pressure compacted, nor heat fused, nor agglomerated by means of an organic solvent, nor by means of any other post treatment for particle size enlargement.
In addition, the novel particle size distributions of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention may contribute materially to the efficacy with which such particulate solids can be compacted.
Thus, in a preferred group of 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention in which the average particle size is in the range of at least about 175 microns but less than 300 microns, 50% by weight of the particles have a particle size of at least about 180 microns.
In a particularly preferred group of 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention in which the average particle size is in the range of at least about 175 but less than 300 microns, 10 percent by weight of the particles have a particle size of at least about 280 microns, 25 percent by weight of the particles have a particle size of at least about 240 microns, 50 percent by weight of the particles have a particle size of at least about 180 microns, 75 percent by weight of the particles have a particle size of at least about 100 microns, and 90 percent by weight of the particles have a particle size of at least about 45 microns. It is perhaps worth noting that the foregoing weight percentages typically correspond also to volume percentages.
Thus, in a preferred group of 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention in which the average particle size is in the range of 300 to about 700 microns, 50% by weight of the particles have a particle size of at least about 350 microns.
In a particularly preferred group of 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention in which the average particle size is in the range of 300 to about 700 microns, 10 percent by weight of the particles have a particle size of at least about 500 microns, 25 percent by weight of the particles have a particle size of at least about 440 microns, 50 percent by weight of the particles have a particle size of at least about 350 microns, 75 percent by weight of the particles have a particle size of at least about 120 microns, and 90 percent by weight of the particles have a particle size of at least about 50 microns.
As also described above, this invention provides products in which one or more of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention are converted into granules, tablets, briquettes, pucks, or any other larger sized product, however produced. Typical operations of this type have been described above. Other procedures include, for example, mixing the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention with other dialkylhydantoins and if desired, heat fusing the resultant mixtures, such as described in U.S. Pat. Nos. 4,560,766 and 4,654,424. Similarly, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can be utilized in combination with 1,3-bromochloro-5-methyl-5-propylhydantoin as a binder as described in published PCT Application WO 97/43264.
While there are no hard and fast rules governing differentiation with respect to size among granules, tablets, briquettes, and pucks, typically granules are regarded as being particles ranging in size from about 80 to about 3 U.S. standard mesh size. Tablets typically fall in the range of from about 0.5 to about 1.0 inch in diameter and about 0.5 to about 1.0 inch in thickness. Briquettes will normally range in size from about 0.5 to about 4.0 inches in length, from about 0.5 to about 4.0 inches in width, and from about 0.5 to about 2.5 inches in thickness. Pucks are normally disc-shaped objects having a diameter up to about 3.0 inches and a thickness in the range of about 0.5 to about 1.0 inch. It will be understood and appreciated however, that these dimensions are not intended to unduly limit the scope of this invention.
If desired, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can be formulated with suitable excipients such as binders, lubricants, disintegrants, and mold release agents. Other optional ingredients which may be used in the formulation of products from the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention include fragrances, stabilizers, corrosion inhibitors, dyes, other biocidal agents, surfactants, effervescents, diluents, builders, chelating agents, and the like. Such ancillary materials should of course be compatible with 1,3-dibromo-5,5-dimethylhydantoin and not interfere in any material way with the excellent performance characteristics of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention. The amount(s) of such ancillary materials used should of course be sufficient to serve the purpose for which it is, or they are, being used. At the same time, the amount used should not materially detract from the physical, mechanical, or performance properties of the formulated product.
As indicated above, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can be compacted with or without use of a binder. In the practice of this invention it is preferred to conduct the compaction in the absence of a binder. Commonly-owned co-pending application Ser. No. 09/487,816, filed Jan. 18, 2000, relates in part to the compaction of 1,3-dihalo-5,5-dimethylhydantoins using novel binders described therein.
The following Examples are presented to illustrate the practice of, and advantages made possible by, this invention. These Examples are not intended to limit, and should not be construed as limiting, the scope of this invention to the particular operations or conditions described therein. Examples 1- 8 illustrate how the larger average particle sized 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention can be prepared. In Examples 1-8, pH was monitored by use of a pH meter, and bromine was fed using a Cole-Parmer Masterflex computerized drive and Easy-Load(copyright) pump head. When the continuous operations of Examples 6 and 7 were conducted, the resulting reaction slurry was collected manually and intermittently from the bottom of the reactor. Each fraction was collected in a 500 mL flask.
All particle size determinations referred to in the following Examples were determined by use of a Coulter(copyright) LS Particle Size Analyzer. The analyzer was equipped with an LS 230 small volume module and a Fraunhofer PIDS (Polarization Intensity Differential Scattering) detector switched to the xe2x80x9cOnxe2x80x9d position. The determinations are performed at room temperature with a run time of 1 minute per sample. Prior to conducting the particle size determination, and whenever the sample appears to contain particles adhering to each other, the sample is subjected for 15xc2x11 seconds to sonication using a Sonicor Model SC-100T apparatus to ensure that the particle size measurements are on individual particles of the product, rather than temporarily agglomerated particles. Although particle size determinations can be conducted using any procedure and particle size analysis equipment that give accurate particle size measurements of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids, if there is any significant discrepancy in results from one procedure to another and/or in results using one particle size analysis equipment versus another, the procedure and particle size analysis equipment described in this paragraph should be used as described.